The Effect of Glycerol Addition As Plasticizer in Spirulina Platensis Based Bioplastic

E3S Web of Conferences 67, 03048 (2018) https://doi.org/10.1051/e3sconf/20186703048 3rd i-TREC 2018

The effect of glycerol addition as plasticizer in Spirulina platensis based bioplastic

Dianursanti1,*, Misri Gozan1, and Citra Noviasari1

1Department of Chemical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Baru, 16424, Depok

Abstract. Bioplastic is one of the breakthroughs in the effort to reduce plastic waste. The bioplastic can be produced from microalgae with a high protein content, such as Spirulina platensis. The aim of this research was to produce S. platensis-based plastic with mechanical properties that mimics the commercial plastic bags. The microalgae were mixed with polyvinyl and maleic anhydride as compatibilizer to strengthen the bond between the microalgae and polymer. Glycerol was added as plasticizer to increase the flexibility. Observation was carried out on tensile strength and elongation of bioplastic with a variation of 15, 20, 25, and 30 wt% of glycerol content. The results show that the optimum plasticizer composition for this S. platensis-based bioplastic film was 30 wt%, which shows the tensile strength at 27.7 kgf/cm2 and elongation at 66%. The tensile strength was very close to that of commercial plastic bags. The elongation property should be improved in order to be utilized for plastic bags. However, this bioplastic is very suitable for food, pharmacy, and cosmetic packaging materials that do not need high elongation.

1 Introduction [9]. In this research, bioplastics were produced by blending the PVA with biopolymer. Microalgae is a promising renewable feedstock to There are three main categories of renewable produce biofuel, biochemistry, and high value product [1]. biopolymer, one of which is protein [8]. Spirulina The main advantages of using microalgae are its platensis has high potential to act as filler in bioplastic characteristics such as ease of cultivation, does not take a composite production because of its high protein content, long time for cultivation, and only need small area which is around 57% [2]. Spirulina platensis is a spiral compared to terrestrial crops [2]. Microalgae also have the cyanobacteria, also has chlorophyll and 50 – 70% protein ability to reduce high amount of CO2 in the atmosphere content [10]. Spirulina platensis can be cultivated in through oxygenic photosynthesis [3-4]. Microalgae has freshwater, brackish water, and sea water [10]. Due to its the potential to act as filler in the production of polymer small cell size, protein in Spirulina platensis do not need matric composite [5]. The utilization of microalgae as to be extracted to be utilized so it reduces cost [8]. filler in polymer matrix composite production is fairly Therefore, in this research we do not extract the protein considerable, such as PVC-Chlorella, PLA-algae, PE- from microalgae. The number of microalgae used in this Chlorella, PBS-Spirulina, etc [5-8]. The purposes of research was approximately 56% and PVA used was using microalgae as filler are to reduce cost and reduce approximately 27%. The addition of microalgae until a CO2 concentration in the atmosphere [3-5]. particular composition to PVA can improve the In the last few years, polyvinyl alcohol (PVA) attracts mechanical properties of PVA [5;9]. The price of attention to commercial application because of its Spirulina platensis powder quoted from online properties that have high tensile strength, biodegradable, marketplace is approximately 250 thousand Indonesian and soluble in water so PVA is used as feedstock in Rupiah per kilogram. By blending PVA with Spirulina composite production [1]. Utilization of PVA is ranging platensis, material cost in plastic production can be from food packaging, construction, electronics, etc. Based reduced. The composition of Spirulina platensis below on the market research by Grand View Research, the was obtained from the packaging. number of PVA market in United States was estimated at Other materials needed in bioplastic production are 172.8 kilo tons in 2016 and it is expected to grow at a plasticizer and compatibilizer. Plasticizer is a low Compound Annual Growth Rate (CAGR) of 5.4% from molecular weight non-volatile substance used as additive 2017 to 2025. The price of PVA quoted from Sigma to improve flexibility [11]. Because PVA is brittle, Aldrich is approximately 4 million Indonesian Rupiah per plasticizer is needed to increase the flexibility of the kilogram. In attempt to reduce this PVA demand, it can bioplastic film [12]. Bioplastic produced from be blended with biopolymer. PVA is suitable to be polyethylene/Spirulina platensis/glycerol mixture has the blended with biopolymer because of its high polarity, can highest tensile load with the concentration of glycerol at be manipulated water solutions, and is also biodegradable 11% [2]. In the concentration range between 0 – 50%, the incorporation of glycerol did not significantly reduce film

* Corresponding author: [email protected]/[email protected]

© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). E3S Web of Conferences 67, 03048 (2018) https://doi.org/10.1051/e3sconf/20186703048 3rd i-TREC 2018

strength but enhanced their flexibility [11]. 30 min, at the temperature of 100oC. The filler produced Compatibilizer increases the interfacial adhesion in was in the shape of viscous suspension. The amount of heterogenous polymer blends resulting in better glycerol was varied at 15 wt% (0.6 mL), 20 wt% (0.8 mL), mechanical properties [13]. Dispersion between PVA and 25 wt% (1.0 mL), and 30 wt% (1.2 mL). microalgae is poor so composite with 40 – 50% filler underwent mechanical properties decrease [9]. The use of 2.4 Preparation of bioplastic film compatibilizer can improve interfacial interaction between PVA and microalgae. Plasticizer and The compatibilizer and filler were then mixed under compatibilizer can increase mechanical properties of the stirring for 20 min, at the temperature of 120oC. The bioplastic produced. mixture was stored for 1 day. The molding to make the bioplastic was made of glass, with 20 cm x 15 cm Table 1. Composition of Spirulina platensis dimension. Mineral oil was dabbed on the molding (wt%) surface to make it easier to remove the bioplastic film Protein 60 produced. After 1-day storage, the mixture was stirred and o Lipid 6 heated at 120 C for 15 min before it was poured onto the molding. After that, the mixture was heated in an oven at Fatty Acid 265 mg /10 gr o Amino Acid 2410 mg /10 gr 100 C for 15 min. The bioplastic film was allowed to cool Vitamin A 23000 IU at room temperature before removed from the molding. Vitamin B1 – B3 2.3 mg /10 gr Vitamin B6 & B12 112 mcg 2.5 Mechanical properties Vitamin E 4 IU Phycocianin 20% Mechanical properties of the bioplastic film that were Chlorophyll 1.5% analysed were tensile strength and elongation according to ASTM D882. Tensile strength is the maximum load B-Carotenoids 0.15% where the specimen can hold its shape before failure. Pantothenic Acid 4 mg / 100 gr Elongation is the ratio between maximum length of Folic Acid 100 mcg / 100 g specimen before failure and its initial strength. These Polysaccharide 0.4 g / 100 gr characteristics usually showed in a stress-strain diagram. These properties were obtained by using Universal Tester. 2 Experimental Section The sample was pulled until it was torn and these properties were measured by using extensometer. Mechanical properties of the bioplastic produced were 2.1 Materials compared with mechanical properties of traditional plastic bag. Bioplastics was prepared by using PVA from PT. Brataco Co., with molecular weight 37,000 g/mol. Spirulina platensis powder was produced by Polaris, with protein 3 Results and Discussions content at 60%. Plasticizer used was glycerol for analysis with 99.5% purity from Sigma-Aldrich. Compatibilizer Tensile strength and elongation of the sample were used was pure maleic anhydride (MAH) for synthesis with obtained at Center for Chemical and Packaging, Jakarta, 99% purity from Sigma-Aldrich. Pure potassium and the test refers to ASTM D882. There are 4 samples in  total. The sample dimension was 20 cm x 10 cm. The peroxodisulfate (KPS) 99% and dimethyl sulfoxide 2 (DMSO), the initiators for compatibilizer, were bought tensile strength unit was kgf/cm and the elongation has from Sigma-Adrich. Mineral oil was used to make no unit but it is shown in percentage. The results of the removing the bioplastic from the molding easier. tests were illustrated in Figure 1 and 2. Fig.1 shows that in this research, the concentration of plasticizer is inversely proportional with the tensile 2.2 Preparation of compatibilizer strength of bioplastic film. The tensile strength of bioplastic film shown are 30.8 kgf/cm2 (15 wt%), 29.6 Maleic anhydride 0.15 grams, 2.5 grams polyvinyl kgf/cm2 (20 wt%), 28.3 kgf/cm2 (25 wt%) and 27.7 alcohol, and 15 mL dimethyl sulfoxide were mixed under kgf/cm2 (30 wt%). A 5% increase of plasticizer content stirring for 120 min, at the temperature of 100oC, and decreased the tensile strength of bioplastic film by 1.2 yielded viscous suspension. Potassium peroxodisulafate kgf/cm2. With 10% increase of plasticizer content, the was then added in the amount of 0.0125 grams and mixed tensile strength of bioplastic film decreased by 2.5 under stirring for 60 min, at the temperature of 120oC. kgf/cm2. By adding the plasticizer content by 15%, the tensile strength of bioplastic film decreased by 3.1 2.3 Preparation of filler kg/cm2. It can be concluded that with the addition of 1.2 mL glycerol, the tensile strength of bioplastic film Selected amount of glycerol was added into 15 mL of decreased insignificantly. These decreases of tensile distilled water and stirred for 10 min, at the temperature strength can be described by the replacement of o of 60 C. Then, 5 grams of Spirulina platensis microalgae intermolecular bond between PVA molecule with was added into the mixture and mixed under stirring for intermolecular bond between PVA and glycerol [14].

2 E3S Web of Conferences 67, 03048 (2018) https://doi.org/10.1051/e3sconf/20186703048 3rd i-TREC 2018

Therefore, the strength of the bond decreased which result glycerol, the elongation of bioplastic film increased in the material became easier to fail. However, the sharply. decrease of tensile strength is small because the As mentioned before, the intermolecular bonds intermolecular bond between PVA molecule and between PVA molecules were replaced by intermolecular intermolecular bond between PVA and glycerol are both bonds between PVA and glycerol molecules. This change hydrogen bonds. The tensile strength of commercial of intermolecular bonds caused the reduction of stiffness plastic bag is 26.4 kgf/cm2 [15]. It can be seen that all and increased film flexibility [14]. Therefore, the bioplastic films have higher tensile strength. Therefore, elongation of bioplastic film produced were increased as based on its tensile strength, bioplastic film of this well. The elongation of commercial plastic bag is 222.5% research can be used as commercial plastic bag. [15]. The elongation of bioplastic film in this research were below this number. Therefore, the bioplastic film in this research cannot be used as commercial plastic bag. However, it can be used in other applications, such as packaging for food, pharmacy, and cosmetic that do not need high elongation, which is around 20% [16].

4 Conclusion As mentioned, Spirulina platensis is one of the promising biopolymer materials because of its high protein content. The addition of glycerol as plasticizer in Spirulina platensis-based bioplastic resulted in an improvement of properties of the bioplastic, which is elongation. In order to get similar properties between bioplastic and commercial plastic bag, an optimum addition of glycerol is obtained at 30 wt%. The mechanical properties of bioplastic film with 30 wt% glycerol obtained was 27.7 kgf/cm2 tensile strength and 66% elongation. The lowest Fig 1. Tensile strength of bioplastic film with various glycerol elongation was obtained from addition of 15 wt% (plasticizer) content. glycerol, which was 15%. Although bioplastic film from Spirulina platensis had higher tensile strength than commercial plastic bag, the elongation is lower. However, this bioplastic film showed promising properties to be used in other application, such as packaging for food, pharmacy, or cosmetic.

The authors gratefully thank the financial support from Universitas Indonesia through the Publikasi International Terindeks untuk Tugas Akhir Mahasiswa (PITTA) grant (No. 2416/UN2.R3.1/HKP.05.00/2018).

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